Red Bull has hit reverse gear after boss Christian Horner suggested Mercedes' no-sidepod innovation revealed in Bahrain on Thursday is illegal.

Even F1 managing director Ross Brawn admits that the radical concept, also complete with controversial wing-like crash structure mounts for the side mirrors, came out of left field.

"It's a very extreme interpretation of the regulations and inevitably there is going to be a lot of debate," he said.

However, Brawn also said the idea is "impressive", representing the "great thing" about innovation in Formula 1.

"I think the regulators are ok with it so far but of course a team may come in and raise an objection that the FIA have to consider and then you have a problem," he said.

Indeed, Mercedes' team nemesis Red Bull was quick to raise the spectre of a potential protest, with Horner telling Germany's Auto Motor und Sport that he has concerns.

"The new Mercedes violates the spirit of the regulations," he told correspondent Michael Schmidt. "For us, some parts are not legal.

"These are not mirror mounts, but two wings. They also have vertical baffles built on top. They have nothing to do with the mirror mount.

"From our point of view, Mercedes went a step too far," Horner added.

However, while Schmidt protested that the comments were genuine, it wasn't long before both Red Bull and Horner were denying they were ever uttered.

"Christian Horner has not given any interviews regarding Mercedes' car," said a team spokesman.

Horner confirmed: "I was slightly surprised to be reading comments that I'm supposed to have been making but there we go."

But even Ferrari boss Mattia Binotto admitted his concerns, revealing that the shape of the wing-like mirror mounts in particular "surprised me very much".

"We have always argued before that mirrors should not perform any aerodynamic function," he said. "They should only be used to look backwards.

"We don't want teams designing mirrors that look like spaceships. I don't think that's what Formula 1 needs," the Italian added.

However, Mercedes' Toto Wolff insists the Brackley based team checked the solutions' legality by "exchanging CAD data" and consulting closely with the FIA.

"It is clear that sometimes when you come with an innovation, it creates the kind of debate that we're having here," said the Austrian. "That's why that was expected.

"But I think the FIA and Formula 1 will for sure handle that with diligence, in the spirit of the sport."

Horner, meanwhile, suggested that Red Bull's biggest innovations will only be seen once Formula 1 reconvenes at the same Bahrain circuit next weekend for the first race of 2022.

"The car we have here hasn't changed much from Barcelona," he said. "Next week will be very different."

World champion Max Verstappen, who called Mercedes' latest innovations "ugly", agreed: "Of course we will also have upgrades.

"Not at the moment, but they will come."